Year	Percent
1999-01-01	80.550
2000-01-01	79.950
2001-01-01	79.900
2002-01-01	79.600
2003-01-01	79.500
2004-01-01	80.125
2005-01-01	79.825
2006-01-01	80.550
2007-01-01	80.075
2008-01-01	80.675
2009-01-01	80.225
2010-01-01	79.350
2011-01-01	79.250
2012-01-01	78.650
2013-01-01	78.125
2014-01-01	78.100
2015-01-01	78.450
2016-01-01	79.950
2017-01-01	78.875